Continuity Not Satisfied?

fluid23 · August 13, 2014, 12:39

I am running what should be a simple and straight forward case which consists of a large inlet pipe which branches off into 3 smaller outlet pipes. I have set solution goals to monitor mass flow in to and out of the system. However, there is a 25% discrepancy between in mass flow in and out. Oddly, if I sum 2 of the outlet flows I get the same value as reported for the inlet flow. I am not sure what to make of this since continuity should be satisfied, it being a fundamental concept in the N-S equations and all.
Anyone have any idea why this would be the case? I hope it's a setup error and Solidworks Flow Simulation isn't as awful as it appears to be.

fluid23 · August 13, 2014, 14:28

The problem seems to have been a bad goal definition. I am not really sure how that could be, but I deleted all of my goals then reapplied them and started getting values that agreed. I did nothing different, to my knowledge so it could be a bug. If anyone else experiences something like that, I would be curious to know.

Boris_M · August 14, 2014, 09:31

Hi Matt,

Don't know, never experienced anything like that. Maybe you missed a surface when you applied it or if it remeshed, it solved the problem and there was something wrong with the mesh before. Maybe from an old boundary condition case or something like that.

Boris

August 13, 2014, 12:39	Continuity Not Satisfied?	#1
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	I am running what should be a simple and straight forward case which consists of a large inlet pipe which branches off into 3 smaller outlet pipes. I have set solution goals to monitor mass flow in to and out of the system. However, there is a 25% discrepancy between in mass flow in and out. Oddly, if I sum 2 of the outlet flows I get the same value as reported for the inlet flow. I am not sure what to make of this since continuity should be satisfied, it being a fundamental concept in the N-S equations and all. Anyone have any idea why this would be the case? I hope it's a setup error and Solidworks Flow Simulation isn't as awful as it appears to be.

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August 13, 2014, 14:28		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	The problem seems to have been a bad goal definition. I am not really sure how that could be, but I deleted all of my goals then reapplied them and started getting values that agreed. I did nothing different, to my knowledge so it could be a bug. If anyone else experiences something like that, I would be curious to know.

August 14, 2014, 09:31		#3
Boris_M Disabled Join Date: Jul 2009 Posts: 616 Rep Power: 23	Hi Matt, Don't know, never experienced anything like that. Maybe you missed a surface when you applied it or if it remeshed, it solved the problem and there was something wrong with the mesh before. Maybe from an old boundary condition case or something like that. Boris